NFSv4: Fix a race in NFSv4.1 server trunking discovery

We do not want to allow a race with another NFS mount to cause
nfs41_walk_client_list() to establish a lease on our nfs_client before
we're done checking for trunking.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/client.c

@@ -433,7 +433,7 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat
 
 static bool nfs_client_init_is_complete(const struct nfs_client *clp)
 {
-	return clp->cl_cons_state != NFS_CS_INITING;
+	return clp->cl_cons_state <= NFS_CS_READY;
 }
 
 int nfs_wait_client_init_complete(const struct nfs_client *clp)

fs/nfs/nfs4client.c

@@ -621,6 +621,9 @@ int nfs41_walk_client_list(struct nfs_client *new,
 	spin_lock(&nn->nfs_client_lock);
 	list_for_each_entry(pos, &nn->nfs_client_list, cl_share_link) {
 
+		if (pos == new)
+			goto found;
+
 		if (pos->rpc_ops != new->rpc_ops)
 			continue;
 
@@ -639,10 +642,6 @@ int nfs41_walk_client_list(struct nfs_client *new,
 			prev = pos;
 
 			status = nfs_wait_client_init_complete(pos);
-			if (pos->cl_cons_state == NFS_CS_SESSION_INITING) {
-				nfs4_schedule_lease_recovery(pos);
-				status = nfs4_wait_clnt_recover(pos);
-			}
 			spin_lock(&nn->nfs_client_lock);
 			if (status < 0)
 				break;
@@ -668,7 +667,7 @@ int nfs41_walk_client_list(struct nfs_client *new,
 		 */
 		if (!nfs4_match_client_owner_id(pos, new))
 			continue;
-
+found:
 		atomic_inc(&pos->cl_count);
 		*result = pos;
 		status = 0;

fs/nfs/nfs4state.c

@@ -346,9 +346,19 @@ int nfs41_discover_server_trunking(struct nfs_client *clp,
 	status = nfs4_proc_exchange_id(clp, cred);
 	if (status != NFS4_OK)
 		return status;
-	set_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
 
-	return nfs41_walk_client_list(clp, result, cred);
+	status = nfs41_walk_client_list(clp, result, cred);
+	if (status < 0)
+		return status;
+	if (clp != *result)
+		return 0;
+
+	set_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
+	nfs4_schedule_state_manager(clp);
+	status = nfs_wait_client_init_complete(clp);
+	if (status < 0)
+		nfs_put_client(clp);
+	return status;
 }
 
 #endif /* CONFIG_NFS_V4_1 */